How does Miller 211 handle thick materials out of position? Structural H-beams

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The dual sheild isn't the problem per say, but its the gas mix. The guns are rated at 100% with CO2 and less than that with mixed gasses. So when i use CO2 with the co2 my gun still gets hot but it gets hot quicker with the 75/25. No granted i am in a industrial setting as i use it all day, but as cruizer said you will be hitting your welders duty cycle pretty quick with either gas or wire...Bob

The tables on the right hand side of the page give a straightforward overview of how much amperage a given filler metal can deliver, and how much amperage is needed to have a reasonable chance of achieving good penetration into base metal of a given thickness. What most welders don't consider is that a small wire cannot deliver an unlimited amount of current. For 0.030" wire, the max current that wire can carry is about 145 amps. You need about 340 inches per minute of wire feed speed to get proper short circuit performance(crisp bacon frying sound) at that amperage. If you turn up the wire feed speed beyond 340 IPM, you don't get much, if any, more current delivered to the weld puddle with 0.030" wire. So no more heat, or ability to fuse the weld bead into the base metal. All you get is more metal on the plate, stubbing of the wire, spatter, and generally uglier looking welds.

Turning the wire feed speed down for better control can deliver insufficient current or heat to the puddle. What you get is a better looking weld that lays on the base metal like frosting on a cake. It looks good, but it could fall right off at the least convienent moment.

These recomendations in the tables are for flat or horizontal single pass fillet welds, lap welds, or square groove butt joints with minimal root opening. If you're dealing with material thicker than 1/8", beveling the material, and making 2 or more passes, or filling wide gaps, that changes things.

You'll have to learn how much to turn down the machine settings below what's shown in the tables for a good root pass in an open root joint. AND, you'll need to learn how much to turn up the machine above the settings recommended for all subsequent passes in order to guarantee 100% fusion on all the later fill passes applied to a joint.

This is why you can't weld really thick material with really small wire. Eventually, the weld deposit is so thick, that no matter how high you turn up the wire feed speed, you can't deliver enough heat energy to the material to get good fusion. Exactly when all this breaks down depends on many variables; how hot the base metal is, how fast you travel while welding, how massive the piece is you're welding(how fast heat conducts away from the weld joint).

But at some point thicker wire needs to be used. The tables are probably on the conservative side of telling you when you need to move up or down in wire size, since novices are the ones most likely using them and their welding skills are not good enough to wring 100% of the performance possible out of the welding process.

The rules change when you move to higher powered welding machines that are capable of delivering higher voltage and current. With 250+ amp machines and the correct shielding gases, you can switch from short circuit transfer to spray transfer. Spray or pulsed spray transfer changes the rules completely. But machines like the MM211 are limited to short circuit transfer, so there's not much point in going into the details about spray transfer MIG welding in this topic.

Destructive testing can be as simple as welding two plates of the correct thickness in a T shape with a single fillet weld on one side. Then clamp in a vise and beat on vertical plate opposite of the weld side until it bends over teh weld and breaks. Or use the vise to fold the plates over. Using a hyraulic press is generally faster and easier. Seperate the pieces and look at the root of the weld; the plate were the two plates met. There should be no visible signs of the original base metal at the root. If there are, there is lack of fusion.

The fillet weld should extend onto each piece of base metal about as much as the thickness of the base metal. For example, for 1/4" plate the weld should extend on to the horizontal and vertical plates 1/4" from where they meet. The visible face of the weld bead will be about 3/8" wide. this will generally create a weld joint stronger than the steel used in the base metal. You should be able to make a weld on 3/16" or 1/4" plate using your MM211 with 0.035" wire and gas, in a single flat or horizontal pass. You may use 2 or even 3 passes thicker material if you feel comfortable traveling faster, and you don't mind taking more time to complete the welds. More passes will mean more distortion too, so keep that in mind.

Weld your test plates in the same physical position as you plan on welding the finished pieces. Adjust voltage amperage/wire feed speed, and technique until you find a combination that gives you 100% penetration. Note those settings and techniques, and repeat them when you make your finished welds.

It's a tremendous amount of work, but this is some of what Pros will do when confronted by a difficult weld they've never attempted before, especially on a weld joint that is critical. There's 75+ years of history behind arc welding, and a lot of information on welding procedures that work consistently. This kind of exhaustive testing doesn't happen as often any more as lots of welded connections and procedures are well documented. Structural engineers, mechanical engineers, and such tend to rely on these well-tested and understood joint designs and welding procedures when designing and building structural steel, piping, etc. so they don't have to perform all this destructive testing. AWS calls these pre-qualified welding procedures. If you've ever looked at a welded structure, and thought, "there's got to be a simpler, faster way to get that built", odds are it was designed in a way to avoid having to qualify new welding procedures and joint designs. It's a lot of work to invent a special, unique joint or use a revolutionary welding process or procedure.

Originally Posted by clint738

A_DAB_will_do,

Thank you for your input. The reason I come here is for input from professionals who do this for a living. I don't care if .035" wire is harder to run, if it what is required to have proper penetration, then I will learn to use it.

My millermatic 140 I sold I always used .030 wire, but I don't see how thicker wire will be much harder since it is just laying down more wire at once.

I do plan on destructive testing my welds. Any tips on how to do this? Will probably want to test them with 1/4" plate since it will be close to the H-beam thicknesses.

Pretty sure I wouldn't use the 211 for ANYTHING structural. Now the 211 should be able to push 035 mild steel, as it needs 185 amps to properly weld. However you will be pretty much maxed out voltage and wire speed (amperage). So you'll hit your duty cycle quite a bit.

Why would you NOT recommend ANYTHING structural for the 211?

It states first page of the spec sheet:
"Welds thickest material in its class!The Millermatic® 211 Auto-Set™with
MVP™ has the highest output in its
class. It can weld from 24 ga–3/8 in
(0.8–9.5 mm) mild steel in a singlepass on 230 V."

Why would 1/4" steel be a problem when the specs say 3/8" in a single pass?

185amps seems within the operation range of the welder since it can go to 210amps. I would just have to take my time. There will be a LOT of cutting with an oxy/acet torch so that will give the welder a break from time to time.

This will not be 1/4" to 1/4" steel. I will use 1/4" plate as the anchor plates on the floor and weld the 6" x 9lb/ft .170" thick H-beam to the plate. If I do change up the design and go with 6" x 12lb/ft H-beam the beam thickness will increase to .230".

I was thinking I could upgrade my Mig to a 211 and have enough machine to do this project and still have the ability to mig thinner stuff when needed.

Why would Miller go beyond rating the 211 at 1/4" and say it is rated for 3/8" for single pass welds when the machine is limited to 210 amps and if you go by 1 amp per .001" inch, then 210 falls WAY short of 375?

.035 wire would (being limited to 180amps) be limited to material no thicker than ~ 3/16" steel. There also isn't any gas wire option show bigger than .035"

So Flux core would then be the next option where:
.045 (capable of 250amps) would then be just capable of 1/4" but not 5/16" or 3/8"

Things just don't seem to add up with the charts, since I've never heard of anything thicker than .045 wire, yet 250amps is not enough current using the 1amp = .001" rule to weld 5/16" or 3/8" and I know the 211 is no where near pushing 300amps.

The chart inside the door of my millermatic 251 says that I can run 1/2" on .035 wire. Does it have 500 amps?! nope. A lot of it is just beveling joints to get full penetration. Also, if you look at those ratings and charts and such you will usually see that they are based on butt welds. At the larger thicknesses you will also see some sort of disclaimer about "proper preparation."

The chart inside the door of my millermatic 251 says that I can run 1/2" on .035 wire. Does it have 500 amps?! nope. A lot of it is just beveling joints to get full penetration. Also, if you look at those ratings and charts and such you will usually see that they are based on butt welds. At the larger thicknesses you will also see some sort of disclaimer about "proper preparation."

So if the ratings are beveled butt welded joint, how is this going to handle a 1/4" T-joint. Have never heard of beveling those?